JP2018074000A - Structure used for piezoelectric element, and device using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a piezoelectric structure capable of selectively responding to expansion and contraction deformation and efficiently generating usable electric polarization. SOLUTION: The structure is a structure in which oriented piezoelectric polymers are arranged in a cylindrical shape or a cylindrical shape, and the orientation angle of the piezoelectric polymer with respect to the central axis of the structure is 15 ° to 75 °, and the piezoelectricity is high. The molecule contains a crystalline polymer having an absolute value of the piezoelectric constant d14 of 0.1 to 1000 pC / N when the orientation axis is three axes, and the value of the piezoelectric constant d14 is a positive crystalline polymer. A P-form containing the above and an N-form containing a negative crystalline polymer, and the orientation axis of the portion of the structure having a length of 1 cm is arranged by spiraling in the Z-twist direction. The mass of the body is ZP, the mass of the P-body with the spiral in the S-twist direction is SP, the mass of the N-body with the spiral in the Z-twist direction is ZN, and the mass of the N-body with the spiral in the S-twist direction is SN. Then, when the smaller one of (ZP + SN) and (SP + ZN) is T1 and the larger one is T2, the value of T1 / T2 is 0 to 0.8. [Selection diagram] FIG. 1A

Description

  The present invention relates to a structure used for a piezoelectric element and a device using the same.

Conventionally, many techniques related to elements using piezoelectric materials have been disclosed. For example, Patent Document 1 discloses that an element in which a conductive fiber is coated with a piezoelectric polymer has an excellent electrical response to rubbing. Non-Patent Document 1 discloses an electrical response example of an element in which a piezoelectric polymer is wound in a coil shape, due to expansion and contraction in the axial direction of the coil and torsional deformation around the axis of the coil. Further, Patent Document 2 discloses a fibrous material made of a piezoelectric polymer, and it is described that the piezoelectric material has a large piezoelectric effect when a force (motion) parallel or perpendicular to the fiber axis is applied. ing.
The piezoelectric sheet of Patent Document 3 can output an electric signal by expansion / contraction deformation (stress) with respect to the piezoelectric sheet. However, since it is in the form of a sheet in the first place, it is poor in flexibility, and it cannot be used in a way that it can be freely bent like fibers and cloth.

International Publication No. 2014/058077 JP 2000-144545 A JP 2014-240842 A

Japan Journal of Applied Physics, Vol. 51, page 09LD16

However, the above-described prior art document does not disclose a specific configuration that efficiently generates a piezoelectric signal with respect to a stretching motion, but does not generate a piezoelectric signal with respect to a motion other than the stretching motion. In addition, there is no disclosure of a specific configuration that generates charges having opposite polarities (that is, charges having opposite signs) between the central axis and the outside of the structure in order to increase the use efficiency of piezoelectric signals. Therefore, the performance as a piezoelectric element that can be used for a sensor or an adsorbent is insufficient.
An object of the present invention is to provide a cylindrical or columnar piezoelectric structure capable of selectively responding to expansion / contraction deformation (stress) and efficiently generating usable electrical polarization. is there.

  The inventors have arranged a piezoelectric polymer having a high piezoelectric constant d14 in a specific direction so as to form a cylindrical or columnar structure, so that the cylindrical or columnar structure against expansion and contraction is provided. It has been discovered that charges having opposite polarities can be efficiently generated on the central axis side and the outside of the shape, and the present invention has been achieved.

That is, the present invention includes the following inventions.
(1) A structure in which oriented piezoelectric polymers are arranged in a cylindrical or cylindrical shape, and the orientation angle of the piezoelectric polymer with respect to the direction of the central axis of the cylindrical or cylindrical shape in which the piezoelectric polymers are arranged is Piezoelectric polymer is mainly a crystalline polymer having an absolute value of piezoelectric constant d14 of 0.1 pC / N or more and 1000 pC / N or less when the orientation axis is 3 axes. In addition, the piezoelectric polymer includes a P body containing a crystalline polymer having a positive piezoelectric constant d14 as a main component and an N body containing a negative crystalline polymer as a main component, For the part with the central axis of the structure having a length of 1 cm, the orientation axis is ZP and the orientation axis is spirally arranged in the S twist direction. The mass of the P body is SP, and the orientation axis is helical in the Z twist direction The mass of the N body arranged by winding is ZN, and the mass of the N body arranged by winding the helix in the S twist direction is SN, and the smaller of (ZP + SN) and (SP + ZN) A structure in which T1 / T2 is 0 or more and 0.8 or less, where T1 is T1 and the larger is T2.
(2) The structure according to (1), wherein the piezoelectric polymer contains poly-L-lactic acid or poly-D-lactic acid as a main component.
(3) The structure according to (2), wherein the piezoelectric polymer includes a P body including poly-D-lactic acid as a main component and an N body including poly-L-lactic acid as a main component.
(4) When expansion or contraction is applied in the direction of the central axis of the cylindrical or cylindrical shape where the piezoelectric polymer is disposed, charges having opposite polarities are generated on the cylindrical axial center side and the outer side. The structure according to any one of (1) to (3), which is generated.
(5) The piezoelectric polymer is formed in the form of a braid, a twisted string, a covering thread, or an aligned thread, in the form of a fiber, filament, or tape, (1) to (4) The structure according to any one of claims.
(6) The structure according to any one of (1) to (4), wherein the piezoelectric polymer constitutes only one closed region in a cross section perpendicular to a central axis of a cylindrical or columnar shape. .
(7) An element comprising the structure according to any one of (1) to (6) and a conductor disposed adjacent to the structure.
(8) The element according to (7), wherein the piezoelectric polymer is disposed in a cylindrical shape, and the conductor is disposed at a position of a central axis of the cylindrical shape.
(9) The element according to (8), wherein the conductor is made of a conductive fiber, and the piezoelectric polymer is arranged as a piezoelectric fiber in a braid shape around the conductive fiber.
(10) The element according to (7), wherein the conductor is disposed outside a cylindrical or columnar shape in which a piezoelectric polymer is disposed.
(11) The conductor according to (10), wherein the conductor is made of conductive fiber, and the conductive fiber is arranged in a braid shape around a cylindrical shape or a columnar shape in which the piezoelectric polymer is arranged. Elements.
(12) The element according to any one of (7) to (11),
An output terminal for outputting an electrical signal generated in the conductor in response to an electric charge generated when the piezoelectric polymer is arranged to expand or contract in the direction of the cylindrical or cylindrical central axis;
And an electric circuit for detecting an electric signal output via the output terminal.

  According to the present invention, it is possible to provide a cylindrical or columnar piezoelectric structure capable of selectively responding to expansion / contraction deformation (stress) and efficiently generating usable electrical polarization.

It is a schematic diagram which shows the cylindrical piezoelectric structure which concerns on embodiment. It is a schematic diagram which shows the cylindrical piezoelectric structure which concerns on embodiment. It is a side view which shows the cylindrical piezoelectric structure which concerns on embodiment. It is a side view which shows the piezoelectric structure which concerns on embodiment. It is a schematic diagram which shows the structural example of the braided piezoelectric element which concerns on embodiment. It is a schematic diagram which shows the structural example of the fabric-like piezoelectric element which concerns on embodiment. It is a block diagram which shows a device provided with the piezoelectric element which concerns on embodiment. It is a schematic diagram which shows the structural example of a device provided with the fabric-like piezoelectric element which concerns on embodiment. It is a schematic diagram which shows the other structural example of a device provided with the fabric-like piezoelectric element which concerns on embodiment. It is a microscope picture which shows the cross section of the braided piezoelectric element which concerns on embodiment. It is a microscope picture which shows the cross section of the braided piezoelectric element which concerns on embodiment. It is a microscope picture which shows the cross section of the braided piezoelectric element which concerns on embodiment.

(Cylindrical or cylindrical piezoelectric structure)
The structure (piezoelectric structure) of the present invention includes an oriented piezoelectric polymer, and the oriented piezoelectric polymer is arranged in a cylindrical shape or a cylindrical shape. FIG. 1A is a schematic diagram illustrating a cylindrical piezoelectric structure 1-1 according to the embodiment, and FIG. 1B is a schematic diagram illustrating a cylindrical piezoelectric structure 1-2 according to the embodiment. The outer and inner edges of the cylindrical or columnar bottom surface on which the piezoelectric polymer is disposed are most preferably perfect circles, but may be elliptical or flat.

(Piezoelectric polymer)
The piezoelectric polymer contained in the piezoelectric structure of the present invention is a molded body of uniaxially oriented polymer, and the absolute value of the piezoelectric constant d14 when the orientation axis is triaxial is 0.1 pC / N or more and 1000 pC. A crystalline polymer having a value of / N or less is included as a main component. In the present invention, “including as a main component” refers to occupying 50% by mass or more of the constituent components. In the present invention, the crystalline polymer is a polymer composed of 1% by mass or more of a crystal part and an amorphous part other than the crystal part, and the mass of the crystalline polymer means the crystal part and the amorphous part. And the total mass.
The absolute value of the piezoelectric constant d14 can be suitably used as a crystalline polymer included in the piezoelectric polymer of the present embodiment, with three orientation axes, and a value of 0.1 pC / N or more and 1000 pC / N or less. Examples of the crystalline polymer having cellulose include cellulose, collagen, keratin, fibrin, poly-L-, as shown in “Piezoelectricity of biopolymers” (Eiichi Fukada, Biorheology, Vol. 3, No. 6, pp. 593). Examples include alanine, poly-γ-methyl-L-glutamate, poly-γ-benzyl-L-glutamate, and poly-L-lactic acid. In addition, poly-D-alanine, poly-γ-methyl-D-glutamate, poly-γ-benzyl-D-glutamate, and poly-D-lactic acid, which are optical isomers of these polymers, have opposite signs of d14. However, it is estimated that the absolute value of d14 takes an equivalent value. The value of d14 varies depending on molding conditions, purity, and measurement atmosphere. To achieve the object of the present invention, the crystallinity and crystal orientation of the crystalline polymer in the piezoelectric polymer actually used are used. The uniaxially stretched film having the same degree of crystallinity and crystal orientation is prepared using the crystalline polymer, and the absolute value of d14 of the film is 0 at the actually used temperature. It is only necessary to show a value of 1 pC / N or more and 1000 pC / N or less, and the crystalline polymer contained in the piezoelectric polymer of the present embodiment is not limited to the specific crystalline polymer listed above. Various known methods can be used to measure d14 of a film sample. For example, a sample having electrodes formed by vapor-depositing metal on both sides of a film sample is a rectangle having four sides in a direction inclined 45 degrees from the stretching direction. The value of d14 can be measured by measuring the charge generated in the electrodes on both sides when a tensile load is applied in the longitudinal direction.

  In this embodiment, poly-L-lactic acid and poly-D-lactic acid are particularly preferably used. Poly-L-lactic acid and poly-D-lactic acid, for example, are easily oriented and crystallized by uniaxial stretching after melt film formation, and exhibit piezoelectricity exceeding 10 pC / N as the absolute value of d14. On the other hand, a polarization-treated product of a polyvinylidene fluoride molded product, which is a typical piezoelectric polymer, has a high piezoelectric constant of d33, but the absolute value of d14 is very low and is used as the crystalline polymer of the present invention. I can't.

  Since poly-L-lactic acid and poly-D-lactic acid are reversed in polarization with respect to the same stress, a more preferable structure can be formed by taking a specific arrangement as described later in the present invention. It becomes possible.

  The piezoelectric polymer may be used as an alloy with another polymer that does not exhibit piezoelectricity, but if polylactic acid is used as the main piezoelectric polymer, at least 60% by mass or more based on the total mass of the alloy. And preferably contains polylactic acid, more preferably 70% by mass or more, and most preferably 90% by mass or more.

  Examples of the polymer other than polylactic acid in the case of alloy include polybutylene terephthalate, polyethylene terephthalate, polyethylene naphthalate copolymer, polymethacrylate and the like, but are not limited thereto.

(Orientation angle of piezoelectric polymer)
In the structure in which the piezoelectric polymer of the present invention is arranged in a cylindrical shape or a cylindrical shape, the direction of the cylindrical or cylindrical central axis (hereinafter simply referred to as “central axis”) in which the piezoelectric polymer is arranged The orientation angle θ of the piezoelectric polymer with respect to is 15 ° or more and 75 ° or less. When this condition is satisfied, the piezoelectric effect corresponding to the piezoelectric constant d14 of the crystalline polymer included in the piezoelectric polymer is obtained by applying expansion / contraction deformation (tensile stress and compression stress) in the central axis direction to the piezoelectric structure. Can be efficiently used, and charges of opposite polarity can be efficiently generated on the central axis side and the outside of the piezoelectric structure. From this viewpoint, the orientation angle θ of the piezoelectric polymer with respect to the direction of the central axis is preferably 25 ° or more and 65 ° or less, more preferably 35 ° or more and 55 ° or less, and 40 ° or more and 50 ° or less. More preferably it is. When the piezoelectric polymer is arranged in this way, the orientation direction of the piezoelectric polymer draws a spiral.

In addition, by arranging the piezoelectric polymer in this way, it is possible to prevent shear deformation that rubs the surface of the piezoelectric structure, bending deformation that bends the central axis, and torsional deformation about the central axis. Can prevent a large charge from being generated on the central axis side and the outside of the piezoelectric structure, that is, a piezoelectric structure that selectively generates a large charge with respect to expansion and contraction in the central axis direction.
The orientation angle θ of the piezoelectric polymer with respect to the direction of the central axis refers to the direction of the central axis and the central axis in a parallel projection view of the cylindrical or cylindrical shape in which the piezoelectric polymer is arranged as viewed from the side. The angle formed by the orientation direction of the piezoelectric polymer in the front portion. For example, FIG. 2 is the figure which looked at the cylindrical piezoelectric structure 1 which concerns on embodiment from the side surface. In the example of FIG. 2, the piezoelectric structure is a structure in which a tape of a piezoelectric polymer oriented in the longitudinal direction is spirally wound. The straight line indicating the orientation direction of the tape in front of the central axis CL is OL, and the angle θ formed between CL and OL (0 to 90 degrees) is high in piezoelectricity with respect to the direction of the central axis. This is the orientation angle of the molecule.

  In FIG. 2, since a thin piezoelectric polymer such as a tape is used, the orientation direction of the piezoelectric polymer is substantially the same as the orientation direction of the tape surface observed from the side, but the cylinder is formed using a thick piezoelectric polymer. In the case of forming a piezoelectric structure of a cylindrical shape, or in the case of a cylindrical piezoelectric structure, the internal orientation direction is closer to the central axis direction as it is closer to the central axis than the orientation direction of the surface that can be observed from the side. Therefore, a difference occurs between the surface orientation direction and the internal orientation direction. Moreover, since the orientation direction of the tape surface observed from the side is apparently S-shaped or inverted S-shaped, magnified observation with high magnification is required for accurate observation.

From this point of view, the orientation angle θ of the piezoelectric polymer with respect to the direction of the central axis may be a structure in which fibers, filaments or tape oriented in the longitudinal direction are spirally wound (for example, twisted yarn, covering yarn, braid, etc. ), Measure as much as possible by the following method. A side photograph of the piezoelectric structure is taken and the helical pitch HP of the piezoelectric polymer 2 is measured. As shown in FIG. 3, the helical pitch HP is a linear distance in the central axis direction required for one piezoelectric polymer 2 to travel from the front surface to the back surface again. In addition, after fixing the structure with an adhesive, if necessary, cut out a cross section perpendicular to the central axis of the piezoelectric structure and photograph it to measure the outer radius Ro and the inner radius Ri of the portion occupied by the piezoelectric structure. To do. When the outer edge and inner edge of the cross section are elliptical or flat, the average values of the major axis and the minor axis are Ro and Ri. Ri = 0 when the piezoelectric structure is a cylinder. The orientation angle θ of the piezoelectric polymer with respect to the direction of the central axis is calculated from the following formula.
θ = arctan (2πRm / HP) (0 ° ≦ θ ≦ 90 °)
However, Rm = 2 (Ro ³ −Ri ³ ) / 3 (Ro ² −Ri ² ), that is, the radius of the piezoelectric structure weighted by the cross-sectional area.

  If the piezoelectric polymer has a uniform surface in the side view of the piezoelectric structure and the helical pitch of the piezoelectric polymer cannot be determined, pass the central axis of the piezoelectric structure fixed with an adhesive or the like. Perform a wide-angle X-ray diffraction analysis to transmit X-rays in a sufficiently narrow range so as to pass through the central axis in a direction perpendicular to the fractured plane, determine the orientation direction, and take the angle with the central axis. , Θ.

  For spirals drawn along the orientation direction of a piezoelectric polymer, such as braids and multiple covering yarns, two or more spirals with different spiral directions (S twist direction or Z twist direction) and spiral pitches exist simultaneously. In the case of a piezoelectric structure, the above measurement is performed for each of the piezoelectric polymers having the respective helical directions and helical pitches, and any one of the piezoelectric polymers having the helical direction and the helical pitch satisfies the above-described conditions. is necessary.

However, the polarity (symbol) of the charge generated on the central axis side and the outside with respect to the expansion and contraction in the central axis direction of the piezoelectric structure is determined by arranging the orientation direction of a certain piezoelectric polymer along the S-twisted helix. When the orientation direction of the same piezoelectric polymer is arranged along the Z-twisted helix, the polarities are opposite to each other. Therefore, the orientation direction of a certain piezoelectric polymer is along the S-twisted helix. When it is placed along the Z-twisted helix at the same time as it is placed (for example, when a braid is formed using both a yarn in the S-twisted direction and a yarn in the Z-twisted direction). Since the generated charges with respect to each other cancel each other in the S twist direction and the Z twist direction, it is not preferable. Therefore, as an embodiment of the present invention, the piezoelectric polymer includes a P body including a crystalline polymer having a positive piezoelectric constant d14 as a main component, and an N body including a negative crystalline polymer as a main component. In the portion where the central axis of the piezoelectric structure has a length of 1 cm, the orientation axis is ZP and the orientation axis is spiral in the S twist direction. The mass of the P body arranged by winding the SP is SP, the mass of the N body arranged by winding the spiral in the Z twist direction is ZN, and the mass of the N body arranged by winding the spiral in the S twist direction. When the mass of is Z, the smaller one of (ZP + SN) and (SP + ZN) is T1, and the larger is T2, the value of T1 / T2 is preferably 0 or more and 0.8 or less. It is preferable that it is 0.5 or more. In particular, the piezoelectric polymer includes a P-form containing poly-D-lactic acid as a main component and an N-form containing poly-L-lactic acid as a main component, and the piezoelectric structure has a long central axis of 1 cm. For the portion having a thickness, the mass of the P body arranged with the spiral in the Z twist direction is ZP, the mass of the P body arranged with the spiral in the S twist direction is SP, the orientation axis Z is the mass of the N body arranged in the Z twist direction and Z is the mass of the N body arranged in the S twist direction and the SN is the mass of the N body arranged in the S twist direction, and (ZP + SN) and (SP + ZN) Of these, when T1 is the smaller and T2 is the larger, the value of T1 / T2 is more preferably 0 or more and 0.8 or less, and further preferably 0 or more and 0.5 or less.
Also, a piezoelectric polymer containing crystalline polymers having different d14 signs, such as poly-L-lactic acid and poly-D-lactic acid, is mixed along one of the S-twisted or Z-twisted helices. Arrangement is not preferable because generated charges for expansion and contraction cancel each other and cannot be used efficiently.

(Configuration of piezoelectric structure)
As described above, in the piezoelectric structure according to the present invention, the orientation direction of the piezoelectric polymer is arranged to draw a spiral. Particularly preferred examples of the piezoelectric structure having such an arrangement include twisted yarns, covering yarns, braids using fibers, filaments or tapes in which a piezoelectric polymer is oriented in the longitudinal direction. When using a tape, it is possible to use a tape oriented in a direction other than the longitudinal direction of the tape, a spirally wound tape, or a cylinder molded in parallel with the longitudinal direction and the central axis direction. it can. From the standpoint of improving productivity and degree of orientation, fibers, filaments or tapes that are oriented in the longitudinal direction by stretching, twisting yarns, covering yarns, and braids are more preferable. From the viewpoint of structural stability, braids are especially preferable.

When the piezoelectric structure of the present invention is stretched and deformed in the direction of the central axis, charges having opposite polarities are generated on the central axis side and the outside. The form of use is not particularly limited, and it can be used for operations such as adsorption / desorption of substances, attractive / repulsive force, generation of electromagnetic waves, and electrical stimulation to living bodies. A form in which a conductor is arranged outside and / or is more preferable. In the case where the conductor is disposed outside, it is more preferable that the conductor is disposed so as to cover all the columnar side surface or the cylindrical side surface of the piezoelectric structure in terms of charge utilization efficiency and use as a shield. You may arrange | position an electroconductive body only partially.
From the viewpoint of productivity, bending durability, and structural stability, a braided piezoelectric structure described below is most preferable.

(Braided piezoelectric element)
FIG. 4 is a schematic diagram illustrating a configuration example of a braided piezoelectric structure (hereinafter referred to as a braided piezoelectric element) according to the embodiment.
The braided piezoelectric element 11 includes a core portion 13 formed of a conductive fiber B and a sheath portion 12 formed of a braided piezoelectric fiber A so as to cover the core portion 13. The part 12 is a cylindrical piezoelectric structure in the present invention. The piezoelectric fiber A can contain polylactic acid as a main component.

In the braided piezoelectric element 11, a large number of piezoelectric fibers A densely surround the outer peripheral surface of at least one conductive fiber B. When the braided piezoelectric element 11 is deformed, a stress due to the deformation is generated in each of the many piezoelectric fibers A, thereby generating an electric field (piezoelectric effect) in each of the many piezoelectric fibers A. As a result, the conductive fibers B It is presumed that a voltage change is generated in the conductive fiber B by superimposing the electric fields of a large number of piezoelectric fibers A surrounding the wire. That is, the electrical signal from the conductive fiber B increases as compared with the case where the braided sheath portion 12 of the piezoelectric fiber A is not used. As a result, the braided piezoelectric element 11 can extract a large electric signal even by a stress generated by a relatively small deformation. A plurality of conductive fibers B may be used.
Here, it is preferable that the signal intensity detected via the conductive fiber B serving as the core is more strongly constrained as well as the contact state with the piezoelectric fiber A serving as the sheath does not change. For example, it is possible to obtain a braid that is more strongly constrained by increasing the tension when the piezoelectric fibers are braided by a string making machine. On the other hand, polylactic acid (PLA) fibers are weak in strength and high in friction. Therefore, there are cases where the fiber breaks a single yarn on the yarn path of the string making machine and a beautiful braid cannot be obtained. That is, in the string making process, the fiber is assembled while the fibers are stretched and loosened momentarily by the bobbin accumulator along the path on which the carrier holding the bobbin wound with the fibers moves on the board. It is difficult to string with high tension. However, it has been found that such difficulty can be improved by twisting the PLA fiber. Specifically, it is preferable to perform twist processing on the PLA fiber with a twist number of 10 to 5000 T / m. If it is less than 10 T / m, the effect of twisted yarn cannot be obtained, and if it is greater than 5000 T / m, the fibers are likely to be twisted and troubles during processing are likely to occur. In addition, the angle of the PLA in the orientation axis direction with respect to the deformation in the axial direction of the braid when the braid is formed is not appropriate, and the signal strength may be reduced. The number of twists is more preferably 30 T / m or more, and still more preferably 50 T / m or more. Moreover, as an upper limit of the number of twists, 3000 T / m or less is more preferable, More preferably, it is 1500 T / m or less. The twisting method is not particularly limited, and any known twisting method can be applied. Further, the twisted fiber is preferably heat-treated, and the heat-treated fiber fixes the twisted state and facilitates handling of the fiber. The heat treatment method is not particularly limited, and generally, the temperature of Tg to Tm of the target fiber is preferably selected, and the treatment may be performed under humidity.

  Here, the piezoelectric fiber A preferably contains polylactic acid as a main component. The lactic acid unit in the polylactic acid is preferably 90 mol% or more, more preferably 95 mol% or more, and even more preferably 98 mol% or more.

  In the braided piezoelectric element 11, as long as the object of the present invention is achieved, the sheath portion 12 may be mixed with fibers other than the piezoelectric fiber A, and the core portion 13 may be conductive. Mixing or the like may be performed in combination with fibers other than the fiber B.

The length of the braided piezoelectric element constituted by the core portion 13 of the conductive fiber B and the sheath portion 12 of the braided piezoelectric fiber A is not particularly limited. For example, the braided piezoelectric element may be manufactured continuously in manufacturing, and then cut to a required length for use. The length of the braided piezoelectric element is 1 mm to 10 m, preferably 5 mm to 2 m, more preferably 1 cm to 1 m. If the length is too short, the convenience of the fiber shape will be lost, and if the length is too long, it will be necessary to consider the resistance value of the conductive fiber B.
Hereinafter, each configuration will be described in detail.

(Conductive fiber)
As the conductive fiber B, any known fiber may be used as long as it exhibits conductivity. As the conductive fiber B, for example, metal fiber, fiber made of a conductive polymer, carbon fiber, fiber made of a polymer in which a fibrous or granular conductive filler is dispersed, or conductive on the surface of a fibrous material. The fiber which provided the layer which has is mentioned. Examples of the method for providing a conductive layer on the surface of the fibrous material include a metal coat, a conductive polymer coat, and winding of conductive fibers. Among these, a metal coat is preferable from the viewpoint of conductivity, durability, flexibility and the like. Specific methods for coating the metal include vapor deposition, sputtering, electrolytic plating, and electroless plating, but plating is preferable from the viewpoint of productivity. Such a metal-plated fiber can be referred to as a metal-plated fiber.

  As a base fiber coated with a metal, a known fiber can be used regardless of conductivity, for example, polyester fiber, nylon fiber, acrylic fiber, polyethylene fiber, polypropylene fiber, vinyl chloride fiber, aramid fiber, In addition to synthetic fibers such as polysulfone fibers, polyether fibers and polyurethane fibers, natural fibers such as cotton, hemp and silk, semi-synthetic fibers such as acetate, and regenerated fibers such as rayon and cupra can be used. The base fibers are not limited to these, and known fibers can be arbitrarily used, and these fibers may be used in combination.

  Any metal may be used as long as the metal coated on the base fiber exhibits conductivity and exhibits the effects of the present invention. For example, gold, silver, platinum, copper, nickel, tin, zinc, palladium, indium tin oxide, copper sulfide, and a mixture or alloy thereof can be used.

  When an organic fiber coated with metal having bending resistance is used for the conductive fiber B, the conductive fiber is hardly broken and excellent in durability and safety as a sensor using a piezoelectric element.

  The conductive fiber B may be a multifilament in which a plurality of filaments are bundled, or may be a monofilament composed of a single filament. A multifilament is preferred from the viewpoint of long stability of electrical characteristics. In the case of monofilament (including spun yarn), the single yarn diameter is 1 μm to 5000 μm, preferably 2 μm to 100 μm. More preferably, it is 3 micrometers-50 micrometers. In the case of a multifilament, the number of filaments is preferably 1 to 100,000, more preferably 5 to 500, and still more preferably 10 to 100. However, the fineness and the number of the conductive fibers B are the fineness and the number of the core part 3 used when producing the braid, and the multifilament formed of a plurality of single yarns (monofilaments) is also one conductive. It shall be counted as fiber B. Here, the core portion 3 is the total amount including the fibers other than the conductive fibers.

  If the diameter of the fiber is small, the strength is reduced and handling becomes difficult, and if the diameter is large, flexibility is sacrificed. The cross-sectional shape of the conductive fiber B is preferably a circle or an ellipse from the viewpoint of the design and manufacture of the piezoelectric element, but is not limited thereto.

Moreover, in order to efficiently extract the electrical output from the piezoelectric polymer, the electrical resistance is preferably low, and the volume resistivity is preferably 10 ⁻¹ Ω · cm or less, more preferably 10 ⁻² Ω · cm. cm or less, more preferably 10 ⁻³ Ω · cm or less. However, the resistivity of the conductive fiber B is not limited to this as long as sufficient strength can be obtained by detection of the electric signal.

The conductive fiber B must be resistant to movement such as repeated bending and twisting from the use of the present invention. As the index, one having a greater nodule strength is preferred. The nodule strength can be measured by the method of JIS L1013 8.6. The degree of knot strength suitable for the present invention is preferably 0.5 cN / dtex or more, more preferably 1.0 cN / dtex or more, and further preferably 1.5 cN / dtex or more. 2.0 cN / dtex or more is most preferable. As another index, one having a smaller bending rigidity is preferred. The bending rigidity is generally measured by a measuring device such as KES-FB2 pure bending tester manufactured by Kato Tech Co., Ltd. The degree of bending rigidity suitable for the present invention is preferably smaller than the carbon fiber “Tenax” (registered trademark) HTS40-3K manufactured by Toho Tenax Co., Ltd. Specifically, the bending stiffness of the conductive fiber is preferably 0.05 × 10 ⁻⁴ N · m ² / m or less, and preferably 0.02 × 10 ⁻⁴ N · m ² / m or less. More preferably, it is more preferably 0.01 × 10 ⁻⁴ N · m ² / m or less.

  The optical purity of polylactic acid is preferably 99% or more, more preferably 99.3% or more, and further preferably 99.5% or more. If the optical purity is less than 99%, the piezoelectricity may be remarkably lowered, and it may be difficult to obtain a sufficient electrical signal due to the shape change of the piezoelectric fiber A. In particular, the piezoelectric fiber A preferably contains poly-L-lactic acid or poly-D-lactic acid as a main component, and the optical purity thereof is preferably 99% or more.

  The piezoelectric fiber A containing polylactic acid as a main component is drawn at the time of production and is uniaxially oriented in the fiber axis direction. Furthermore, the piezoelectric fiber A is not only uniaxially oriented in the fiber axis direction but also preferably contains polylactic acid crystals, and more preferably contains uniaxially oriented polylactic acid crystals. This is because polylactic acid exhibits higher piezoelectricity due to its high crystallinity and uniaxial orientation, and the absolute value of d14 is increased.

Crystallinity and uniaxial orientation are determined by homo PLA crystallinity X _homo (%) and crystal orientation Ao (%). As the piezoelectric fiber A of the present invention, the homo PLA crystallinity X _homo (%) and the crystal orientation degree Ao (%) preferably satisfy the following formula (1).
X _homo × Ao × Ao ÷ 10 ⁶ ≧ 0.26 (1)
If the above formula (1) is not satisfied, the crystallinity and / or uniaxial orientation is not sufficient, and the output value of the electric signal with respect to the operation may decrease, or the sensitivity of the signal with respect to the operation in a specific direction may decrease. is there. The value on the left side of the formula (1) is more preferably 0.28 or more, and further preferably 0.3 or more. Here, each value is obtained according to the following.

Homopolylactic acid crystallinity X _homo :
The homopolylactic acid crystallinity X _homo is obtained from crystal structure analysis by wide angle X-ray diffraction analysis (WAXD). In wide-angle X-ray diffraction analysis (WAXD), an X-ray diffraction pattern of a sample is recorded on an imaging plate under the following conditions by a transmission method using an Ultrax 18 type X-ray diffractometer manufactured by Rigaku.
X-ray source: Cu-Kα ray (confocal mirror)
Output: 45kV x 60mA
Slit: 1st: 1mmΦ, 2nd: 0.8mmΦ
Camera length: 120mm
Accumulation time: 10 minutes Sample: 35 mg of polylactic acid fibers are aligned to form a 3 cm fiber bundle.
In the obtained X-ray diffraction pattern, the total scattering intensity Itotal is obtained over the azimuth angle, and here, the integrated intensity of each diffraction peak derived from the homopolylactic acid crystal appearing in the vicinity of 2θ = 16.5 °, 18.5 °, 24.3 °. Is obtained as a sum ΣIHMi. From these values, the homopolylactic acid crystallinity X _homo is determined according to the following formula (2).
Homopolylactic acid crystallinity X _homo (%) = ΣI _HMi / I _total × 100 (2)
Note that ΣI _HMi is calculated by subtracting diffuse scattering due to background and amorphous in the total scattering intensity.

(2) Crystal orientation degree Ao:
Regarding the crystal orientation degree Ao, in the X-ray diffraction pattern obtained by the above wide-angle X-ray diffraction analysis (WAXD), the diffraction peak derived from the homopolylactic acid crystal appearing in the vicinity of 2θ = 16.5 ° in the radial direction is oriented. The intensity distribution with respect to the angle (°) is taken, and the total half-value width Σ _Wi (°) of the obtained distribution profile is calculated from the following equation (3).
Crystal orientation degree Ao (%) = (360−ΣW _i ) ÷ 360 × 100 (3)

  In addition, since polylactic acid is a polyester that is hydrolyzed relatively quickly, in the case where heat and humidity resistance is a problem, a known hydrolysis inhibitor such as an isocyanate compound, an oxazoline compound, an epoxy compound, or a carbodiimide compound is added. Also good. Further, if necessary, the physical properties may be improved by adding an antioxidant such as a phosphoric acid compound, a plasticizer, a photodegradation inhibitor, and the like.

  The piezoelectric fiber A may be a multifilament in which a plurality of filaments are bundled, or may be a monofilament composed of a single filament. In the case of monofilament (including spun yarn), the single yarn diameter is 1 μm to 5 mm, preferably 5 μm to 2 mm, and more preferably 10 μm to 1 mm. In the case of a multifilament, the single yarn diameter is 0.1 μm to 5 mm, preferably 2 μm to 100 μm, and more preferably 3 μm to 50 μm. The number of filaments of the multifilament is preferably 1 to 100,000, more preferably 50 to 50,000, and still more preferably 100 to 20,000. However, the fineness and the number of the piezoelectric fibers A are the fineness and the number per carrier when producing the braid, and the multifilament formed by a plurality of single yarns (monofilaments) is also one piezoelectric. It shall be counted as fiber A. Here, even if a fiber other than the piezoelectric fiber is used in one carrier, the total amount including that is used.

  In order to use such a piezoelectric polymer as the piezoelectric fiber A, any known technique for forming a fiber from the polymer can be employed as long as the effects of the present invention are exhibited. For example, a method of extruding a piezoelectric polymer to form a fiber, a method of melt-spinning a piezoelectric polymer to make a fiber, a method of making a piezoelectric polymer fiber by dry or wet spinning, a method of making a piezoelectric polymer A technique of forming fibers by electrostatic spinning, a technique of cutting thinly after forming a film, and the like can be employed. As these spinning conditions, a known method may be applied according to the piezoelectric polymer to be employed, and a melt spinning method that is industrially easy to produce is usually employed. Furthermore, after forming the fiber, the formed fiber is stretched. As a result, a piezoelectric fiber A that is uniaxially oriented and exhibits large piezoelectricity including crystals is formed.

  In addition, the piezoelectric fiber A can be subjected to treatments such as dyeing, twisting, blending, and heat treatment before making the braided braid as described above.

  Furthermore, since the piezoelectric fiber A may be broken when the braid is formed, the piezoelectric fiber A may be cut off or fluff may come out, so that the strength and wear resistance are preferably high. It is preferably 5 cN / dtex or more, more preferably 2.0 cN / dtex or more, further preferably 2.5 cN / dtex or more, and most preferably 3.0 cN / dtex or more. The abrasion resistance can be evaluated by JIS L1095 9.10.2 B method, etc., and the number of friction is preferably 100 times or more, more preferably 1000 times or more, and further preferably 5000 times or more. Most preferably, it is 10,000 times or more. The method for improving the wear resistance is not particularly limited, and any known method can be used. For example, the crystallinity is improved, fine particles are added, or the surface is processed. Can do. In addition, when processing into braids, a lubricant can be applied to the fibers to reduce friction.

Moreover, it is preferable that the shrinkage rate of the piezoelectric fiber is small from the shrinkage rate of the conductive fiber described above. If the difference in shrinkage rate is large, the braid may bend due to heat treatment during post-fabrication after fabric production or after fabric production or during actual use, or due to changes over time, the flatness of the fabric may deteriorate, or the piezoelectric signal will become weak. May end up. When the shrinkage rate is quantified by the boiling water shrinkage rate described later, it is preferable that the boiling water shrinkage rate S (p) of the piezoelectric fiber and the boiling water shrinkage rate S (c) of the conductive fiber satisfy the following formula (4). .
| S (p) −S (c) | ≦ 10 (4)
The left side of the above formula (4) is more preferably 5 or less, and even more preferably 3 or less.

Further, it is preferable that the contraction rate of the piezoelectric fiber is small in difference from the contraction rate of fibers other than the conductive fibers, for example, insulating fibers. If the difference in shrinkage rate is large, the braid may bend due to heat treatment during post-fabrication after fabric production or after fabric production or during actual use, or due to changes over time, the flatness of the fabric may deteriorate, or the piezoelectric signal will become weak. May end up. When the shrinkage rate is quantified by the boiling water shrinkage rate, it is preferable that the boiling water shrinkage rate S (p) of the piezoelectric fiber and the boiling water shrinkage rate S (i) of the insulating fiber satisfy the following formula (5).
| S (p) −S (i) | ≦ 10 (5)
The left side of the above formula (5) is more preferably 5 or less, and even more preferably 3 or less.

Further, it is preferable that the shrinkage rate of the piezoelectric fiber is small. For example, when the shrinkage rate is quantified by boiling water shrinkage rate, the shrinkage rate of the piezoelectric fiber is preferably 15% or less, more preferably 10% or less, further preferably 5% or less, and most preferably 3% or less. is there. As a means for lowering the shrinkage rate, any known method can be applied. For example, the shrinkage rate can be reduced by relaxing the orientation of the amorphous part or increasing the crystallinity by heat treatment, and the heat treatment is performed. The timing is not particularly limited, and examples thereof include after stretching, after twisting, after braiding, and after forming into a fabric. In addition, the above-mentioned boiling water shrinkage shall be measured with the following method. A casserole of 20 times was made with a measuring machine having a frame circumference of 1.125 m, a load of 0.022 cN / dtex was applied, it was hung on a scale plate, and the initial casket length L0 was measured. After that, this casserole was treated in a boiling water bath at 100 ° C. for 30 minutes, allowed to cool, and again subjected to the above load and hung on the scale plate to measure the length L after shrinkage. Using the measured L0 and L, the boiling water shrinkage is calculated by the following equation (6).
Boiling water shrinkage = (L0−L) / L0 × 100 (%) (6)

(Coating)
The surface of the conductive fiber B, that is, the core portion 13 is covered with the piezoelectric fiber A, that is, the braided sheath portion 12. The thickness of the sheath 12 that covers the conductive fiber B is preferably 1 μm to 10 mm, more preferably 5 μm to 5 mm, still more preferably 10 μm to 3 mm, and most preferably 20 μm to 1 mm. preferable. If it is too thin, there may be a problem in terms of strength. If it is too thick, the braided piezoelectric element 11 may become hard and difficult to deform. In addition, the sheath part 12 said here refers to the layer adjacent to the core part 13. FIG.

In the braided piezoelectric element 11, the total fineness of the piezoelectric fibers A in the sheath 12 is preferably not less than 1/2 times and not more than 20 times the total fineness of the conductive fibers B in the core portion 13, and more than 1 times. 15 times or less, more preferably 2 times or more and 10 times or less. If the total fineness of the piezoelectric fiber A is too small relative to the total fineness of the conductive fiber B, the piezoelectric fiber A surrounding the conductive fiber B is too small and the conductive fiber B cannot output a sufficient electrical signal, Furthermore, there exists a possibility that the conductive fiber B may contact the other conductive fiber which adjoins. If the total fineness of the piezoelectric fiber A is too large relative to the total fineness of the conductive fiber B, there are too many piezoelectric fibers A surrounding the conductive fiber B, and the braided piezoelectric element 11 becomes hard and difficult to deform. That is, in any case, the braided piezoelectric element 11 does not sufficiently function as a sensor.
The total fineness referred to here is the sum of the finenesses of all the piezoelectric fibers A constituting the sheath portion 12. For example, in the case of a general 8-strand braid, it is the sum of the finenesses of 8 fibers.

  In the braided piezoelectric element 11, the fineness per piezoelectric fiber A of the sheath 12 is preferably 1/20 or more and 2 or less the total fineness of the conductive fiber B. It is more preferably 15 times or more and 1.5 times or less, and further preferably 1/10 time or more and 1 time or less. If the fineness per piezoelectric fiber A is too small with respect to the total fineness of the conductive fiber B, the piezoelectric fiber A is too small and the conductive fiber B cannot output a sufficient electric signal. A may be cut off. If the fineness per piezoelectric fiber A is too large relative to the total fineness of the conductive fiber B, the piezoelectric fiber A is too thick and the braided piezoelectric element 11 becomes hard and difficult to deform. That is, in any case, the braided piezoelectric element 11 does not sufficiently function as a sensor.

  In addition, when a metal fiber is used for the conductive fiber B, or when the metal fiber is mixed with the conductive fiber A or the piezoelectric fiber B, the fineness ratio is not limited to the above. This is because, in the present invention, the ratio is important in terms of contact area and coverage, that is, area and volume. For example, when the specific gravity of each fiber exceeds 2, it is preferable that the ratio of the average cross-sectional area of the fiber is the ratio of the fineness.

  Although it is preferable that the piezoelectric fiber A and the conductive fiber B are as close as possible, an anchor layer or an adhesive layer is provided between the conductive fiber B and the piezoelectric fiber A in order to improve the adhesiveness. May be.

  The covering method is a method in which the conductive fiber B is used as a core yarn, and the piezoelectric fiber A is wound around in a braid shape around the conductive fiber B. On the other hand, the shape of the braid of the piezoelectric fiber A is not particularly limited as long as an electric signal can be output with respect to the stress generated by the applied load. A braided string is preferred.

  The shape of the conductive fiber B and the piezoelectric fiber A is not particularly limited, but is preferably as close to a concentric circle as possible. When a multifilament is used as the conductive fiber B, the piezoelectric fiber A only needs to be covered so that at least a part of the surface (fiber peripheral surface) of the multifilament of the conductive fiber B is in contact. The piezoelectric fibers A may or may not be coated on all filament surfaces (fiber peripheral surfaces) constituting the multifilament. What is necessary is just to set suitably the covering state of the piezoelectric fiber A to each internal filament which comprises the multifilament of the conductive fiber B, considering the performance as a piezoelectric element, the handleability, etc.

  The braided piezoelectric element 11 of the present invention does not require an electrode to be present on the surface thereof, so that it is not necessary to further cover the braided piezoelectric element 11 itself, and there is an advantage that malfunction is unlikely.

(Production method)
The braided piezoelectric element 11 of the present invention covers the surface of at least one conductive fiber B with the braided piezoelectric fiber A. Examples of the manufacturing method include the following methods. In other words, the conductive fiber B and the piezoelectric fiber A are produced in separate steps, and the conductive fiber B is wrapped around the conductive fiber B in a braid shape and covered. In this case, it is preferable to coat so as to be as concentric as possible.

  In this case, as preferred spinning and stretching conditions when polylactic acid is used as the piezoelectric polymer for forming the piezoelectric fiber A, the melt spinning temperature is preferably 150 ° C. to 250 ° C., and the stretching temperature is preferably 40 ° C. to 150 ° C. The draw ratio is preferably 1.1 to 5.0 times, and the crystallization temperature is preferably 80 ° C to 170 ° C.

  As the piezoelectric fiber A wound around the conductive fiber B, a multifilament in which a plurality of filaments are bundled may be used, or a monofilament (including spun yarn) may be used. In addition, as the conductive fiber B around which the piezoelectric fiber A is wound, a multifilament in which a plurality of filaments are bundled may be used, or a monofilament (including spun yarn) may be used. Further, the conductive fiber B may be twisted.

  As a preferable form of the coating, the conductive fiber B can be used as a core yarn, and the piezoelectric fiber A can be formed in a braid shape around the conductive fiber B to form a round braid. . More specifically, an 8-strand braid having 16 cores and a 16-strand braid. At this time, it is preferable to use a twisted fiber for the piezoelectric fiber A, but all the piezoelectric fibers may be twisted or a part of them may be twisted. Moreover, the twist direction of the piezoelectric fiber A does not need to be the same direction for all the piezoelectric fibers A to be used. For example, it is possible to use a fiber that rotates in the clockwise direction during stringing, and a fiber that rotates in the counterclockwise direction and a fiber that rotates in the counterclockwise direction. Further, for example, in the case of an 8-strand braid, not all of the 8 need to be piezoelectric fibers, and other fibers can be used as long as the desired signal strength is obtained. Of course, the conductive fibers of the core part and the conductive fibers to be the shield layer may be twisted. However, for example, the piezoelectric fiber A may be shaped like a braided tube, and the conductive fiber B may be used as a core and inserted into the braided tube.

  By the manufacturing method as described above, the braided piezoelectric element 11 in which the surface of the conductive fiber B is covered with the braided piezoelectric fiber A can be obtained.

  Since the braided piezoelectric element 11 of the present invention does not require the formation of an electrode for detecting an electric signal on the surface, it can be manufactured relatively easily.

(Protective layer)
A protective layer may be provided on the outermost surface of the braided piezoelectric element 11 of the present invention. This protective layer is preferably insulative, and more preferably made of a polymer from the viewpoint of flexibility. In the case of providing the protective layer with insulation, of course, in this case, the entire protective layer is deformed or rubbed on the protective layer, but these external forces reach the piezoelectric fiber A, There is no particular limitation as long as it can induce polarization. The protective layer is not limited to those formed by coating with a polymer or the like, and may be a film, fabric, fiber or the like, or a combination thereof.

  The thinner the protective layer is, the easier it is to transmit shear stress to the piezoelectric fiber A. However, if it is too thin, problems such as destruction of the protective layer itself are likely to occur, and preferably 10 nm to 200 μm. More preferably, they are 50 nm-50 micrometers, More preferably, they are 70 nm-30 micrometers, Most preferably, they are 100 nm-10 micrometers. The shape of the piezoelectric element can also be formed by this protective layer.

It is also possible to incorporate an electromagnetic shielding layer into the braid structure for the purpose of noise reduction. The electromagnetic wave shielding layer is not particularly limited, but may be coated with a conductive substance, or may be wound with a conductive film, fabric, fiber, or the like. The volume resistivity of the electromagnetic wave shielding layer is preferably 10 ⁻¹ Ω · cm or less, more preferably 10 ⁻² Ω · cm or less, and still more preferably 10 ⁻³ Ω · cm or less. However, the resistivity is not limited as long as the effect of the electromagnetic wave shielding layer can be obtained. This electromagnetic wave shielding layer may be provided on the surface of the piezoelectric fiber A of the sheath, or may be provided outside the protective layer described above. Of course, a plurality of layers of electromagnetic shielding layers and protective layers may be laminated, and the order thereof is appropriately determined according to the purpose.

Furthermore, a plurality of layers made of piezoelectric fibers can be provided, or a plurality of layers made of conductive fibers for extracting signals can be provided. Of course, the order and the number of layers of these protective layers, electromagnetic wave shielding layers, layers made of piezoelectric fibers, and layers made of conductive fibers are appropriately determined according to the purpose. In addition, as a method of winding, the method of forming a braid structure in the outer layer of the sheath part 12 or covering is mentioned.
When conductors are arranged on the central axis side and the outside of the piezoelectric structure as described above, a piezoelectric polymer (dielectric material) is formed using the conductor on the center axis side and the outer conductor as two electrodes. It can be regarded as a sandwiched capacitor-like piezoelectric element. In order to effectively extract an electrical signal induced by polarization generated in the piezoelectric structure due to deformation, the value of the insulation resistance between these electrodes should be 1 MΩ or more when measured at a DC voltage of 3V. Preferably, it is 10 MΩ or more, more preferably 100 MΩ or more. In addition, the equivalent series resistance value Rs and equivalent series capacitance Cs obtained by analyzing the response when an AC voltage of 1 MHz is applied between these electrodes are also polarized in the piezoelectric structure due to deformation. In order to effectively extract an electrical signal induced in the light and improve responsiveness, it is preferably within a specific value range. That is, the value of Rs is preferably 1 μΩ or more and 100 kΩ or less, more preferably 1 mΩ or more and 10 kΩ or less, further preferably 1 mΩ or more and 1 kΩ or less, and the value of Cs is the length (cm) in the central axis direction of the piezoelectric structure. The value divided by is preferably from 0.1 pF to 1000 pF, more preferably from 0.2 pF to 100 pF, and even more preferably from 0.4 pF to 10 pF.
As described above, when an element including a piezoelectric structure and an electrode can operate in a preferable state, an equivalent series resistance value Rs obtained by analyzing a response when an AC voltage of 1 MHz is applied between these electrodes. Since the value of the equivalent series capacitance Cs takes a value within a specific range, it is also preferable to use these values for the inspection of the piezoelectric structure. Further, the piezoelectric structure can be inspected by analyzing not only the values of Rs and Cs obtained by the analysis using the AC voltage but also the transient response to other electrical stimuli.

(Function)
In particular, the braided piezoelectric element 11 of the present invention provided expansion / contraction deformation (stress) in the central axis direction of the cylindrical piezoelectric structure formed from the sheath 12, that is, in the direction parallel to the conductive fiber B. In this case, a large electric signal can be output efficiently. On the other hand, no large electrical signal is output for torsional deformation, bending, and rubbing deformation.

  Here, it is preferable that the expansion / contraction deformation given to the braided piezoelectric element 11 is given in a range where the fibers in the element do not reach the deformation amount for starting plastic deformation. The amount of deformation depends on the physical properties of the fibers used. However, this does not apply to applications that do not assume repetitive specifications.

(Fabric piezoelectric element)
FIG. 5 is a schematic diagram illustrating a configuration example of a fabric-like piezoelectric element using the braided piezoelectric element according to the embodiment.
The cloth-like piezoelectric element 15 includes a cloth 16 including at least one braided piezoelectric element 11. The fabric 16 is not limited in any way as long as at least one of the fibers (including braids) constituting the fabric is the braided piezoelectric element 11 and the braided piezoelectric element 11 can function as a piezoelectric element. Any woven or knitted fabric may be used. In forming the cloth, as long as the object of the present invention is achieved, weaving, knitting and the like may be performed in combination with other fibers (including braids). Of course, the braided piezoelectric element 11 may be used as a part of a fiber (for example, warp or weft) constituting the fabric, or the braided piezoelectric element 11 may be embroidered or bonded to the fabric. Good. In the example shown in FIG. 5, the fabric-like piezoelectric element 15 has at least one braid-like piezoelectric element 11 and insulating fibers 17 as warps and alternately has conductive fibers 18 and insulating fibers 17 as wefts. Plain woven fabric. The conductive fiber 18 may be the same type as the conductive fiber B or may be a different type of conductive fiber, and the insulating fiber 17 will be described later. Note that all or part of the insulating fibers 17 and / or the conductive fibers 18 may be braided.

  In this case, when the cloth-like piezoelectric element 15 is deformed by bending or the like, the braid-like piezoelectric element 11 is also deformed along with the deformation, so that the cloth-like piezoelectric element 15 is generated by an electric signal output from the braid-like piezoelectric element 11. Can be detected. Since the cloth-like piezoelectric element 15 can be used as a cloth (woven or knitted fabric), the cloth-like piezoelectric element 15 can be applied to, for example, a garment-shaped wearable sensor.

  Further, in the cloth-like piezoelectric element 15 shown in FIG. 5, the conductive fiber 18 intersects and contacts the braided piezoelectric element 11. Therefore, the conductive fiber 18 intersects and covers at least a part of the braided piezoelectric element 11, covers it, and shields at least a part of the electromagnetic wave that goes from the outside toward the braided piezoelectric element 11. Can be seen. Such a conductive fiber 18 has a function of reducing the influence of electromagnetic waves on the braided piezoelectric element 11 by being grounded. That is, the conductive fiber 18 can function as an electromagnetic wave shield for the braided piezoelectric element 11. Thereby, for example, the S / N ratio of the cloth-like piezoelectric element 15 can be remarkably improved without overlapping conductive cloths for electromagnetic wave shielding on and under the cloth-like piezoelectric element 15. In this case, the higher the ratio of the conductive fibers 18 in the wefts (in the case of FIG. 5) intersecting with the braided piezoelectric element 11 is preferable from the viewpoint of electromagnetic shielding. Specifically, 30% or more of the fibers forming the fabric 16 and intersecting the braided piezoelectric element 11 are preferably conductive fibers, more preferably 40% or more, and 50% or more. Further preferred. Thus, in the cloth-like piezoelectric element 15, the cloth-like piezoelectric element 15 with an electromagnetic wave shield can be obtained by inserting conductive fibers as at least a part of the fibers constituting the cloth.

  Examples of the woven structure of the woven fabric include a three-layer structure such as plain weave, twill weave, and satin weave, a change structure, a single double structure such as a vertical double weave and a horizontal double weave, and a vertical velvet. The type of knitted fabric may be a circular knitted fabric (weft knitted fabric) or a warp knitted fabric. Preferable examples of the structure of the circular knitted fabric (weft knitted fabric) include flat knitting, rubber knitting, double-sided knitting, pearl knitting, tuck knitting, floating knitting, single-sided knitting, lace knitting, and bristle knitting. Examples of the warp knitting structure include single denby knitting, single atlas knitting, double cord knitting, half tricot knitting, back hair knitting, jacquard knitting, and the like. The number of layers may be a single layer or a multilayer of two or more layers. Further, it may be a napped woven fabric or a napped knitted fabric composed of a napped portion made of a cut pile and / or a loop pile and a ground tissue portion.

(Multiple piezoelectric elements)
In the fabric-like piezoelectric element 15, a plurality of braid-like piezoelectric elements 11 can be used side by side. For example, the braided piezoelectric elements 11 may be used for all the warps or wefts, or the braided piezoelectric elements 11 may be used for several or a part. Alternatively, the braided piezoelectric element 11 may be used as a warp in a certain portion, and the braided piezoelectric element 11 may be used as a weft in another portion.

  In this way, when forming the fabric-like piezoelectric element 15 by arranging a plurality of braided piezoelectric elements 11, the braided piezoelectric element 11 does not have electrodes on the surface, so that the arrangement and knitting methods can be selected widely. There is an advantage.

  When a plurality of braided piezoelectric elements 11 are used side by side, the distance between the conductive fibers B is short, which is efficient in taking out an electric signal.

(Insulating fiber)
In the cloth-like piezoelectric element 15, insulating fibers can be used for portions other than the braided piezoelectric element 11 (and the conductive fiber 18). At this time, the insulating fiber may be a stretchable material or a fiber having a shape for the purpose of improving the flexibility of the cloth-like piezoelectric element 15.

  In this way, by arranging the insulating fiber in addition to the braided piezoelectric element 11 (and the conductive fiber 18), the operability of the cloth-like piezoelectric element 15 (e.g., ease of movement as a wearable sensor) is improved. It is possible to make it.

As such an insulating fiber, it can be used if the volume resistivity is 10 ⁶ Ω · cm or more, more preferably 10 ⁸ Ω · cm or more, and further preferably 10 ¹⁰ Ω · cm or more.

  Insulating fibers such as polyester fibers, nylon fibers, acrylic fibers, polyethylene fibers, polypropylene fibers, vinyl chloride fibers, aramid fibers, polysulfone fibers, polyether fibers, polyurethane fibers, etc., cotton, hemp, silk, etc. Natural fibers, semi-synthetic fibers such as acetate, and regenerated fibers such as rayon and cupra can be used. It is not limited to these, A well-known insulating fiber can be used arbitrarily. Furthermore, these insulating fibers may be used in combination, or may be combined with a fiber having no insulating property to form a fiber having insulating properties as a whole.

  Also, any known cross-sectional shape fiber can be used.

(Applied technology for piezoelectric elements)
The piezoelectric element such as the braided piezoelectric element 11 or the cloth-like piezoelectric element 15 of the present invention can output the expansion / contraction deformation (stress) in the central axis direction of the braided piezoelectric element as an electric signal, regardless of the state. Therefore, it can be used as a sensor (device) for detecting the magnitude and / or position of the stress applied to the piezoelectric element. Depending on the arrangement method of the braided piezoelectric element in the cloth-like piezoelectric element, the braided piezoelectric element can be expanded and contracted when subjected to deformation or stress such as bending, twisting, pressing, etc. An electrical signal can also be output by deformation or stress such as bending, twisting, or pressing of the piezoelectric element. Further, this electric signal can be used as a power generation element such as a power source for moving other devices or storing electricity. Specifically, power generation by using it as a moving part of a human, animal, robot, machine, etc. that moves spontaneously, power generation on the surface of a shoe sole, rug, or structure that receives pressure from the outside, shape change in fluid Power generation, etc. In addition, in order to generate an electrical signal due to a shape change in the fluid, it is possible to adsorb a chargeable substance in the fluid or suppress adhesion.

  FIG. 6 is a block diagram showing a device 110 including the piezoelectric element 111 of the present invention. The device 110 amplifies an electrical signal output from the output terminal of the piezoelectric element 111 in accordance with an applied pressure with a piezoelectric element 111 (e.g., braided piezoelectric element 11, fabric-like piezoelectric element 15) and, optionally, a pressure. Amplifying means 112, output means 113 for outputting the electric signal amplified by the optional amplifying means 112, and transmitting means 114 for transmitting the electric signal output from output means 113 to an external device (not shown) And an electric circuit. If this device 110 is used, the braided shape applied to the piezoelectric element by the arithmetic processing in the external device (not shown) based on the electrical signal output by the contact with the surface of the piezoelectric element 111, the pressure, and the shape change. The magnitude of expansion / contraction deformation (stress) in the central axis direction of the piezoelectric element and / or the applied position can be detected.

  The optional amplification means 112, output means 113, and transmission means 114 may be constructed, for example, in the form of a software program, or may be constructed by a combination of various electronic circuits and software programs. For example, the software program is installed in an arithmetic processing device (not shown), and the arithmetic processing device operates according to the software program, thereby realizing the functions of each unit. Alternatively, the optional amplification unit 112, output unit 113, and transmission unit 114 may be realized as a semiconductor integrated circuit in which a software program for realizing the functions of these units is written. Whether the transmission method by the transmission unit 114 is wireless or wired may be appropriately determined according to the sensor to be configured. Alternatively, calculation means (not shown) for calculating the magnitude of the stress applied to the piezoelectric element 111 and / or the applied position based on the electrical signal output from the output means 113 may be provided in the device 110. Good. In addition to the amplifying means, known signal processing means such as noise removing means and means for processing in combination with other signals may be used in combination. The order of connection of these means can be appropriately changed according to the purpose. Of course, the electrical signal output from the piezoelectric element 111 may be processed as it is after being transmitted to the external device.

  7 and 8 are schematic views showing a configuration example of a device including the braided cloth-like piezoelectric element according to the embodiment. The amplifying unit 112 in FIGS. 7 and 8 corresponds to that described with reference to FIG. 6, but the output unit 113 and the transmitting unit 114 in FIG. 6 are not shown in FIGS. 7 and 8. When configuring a device including the fabric-like piezoelectric element 15, the lead wire from the output terminal of the core portion 13 (formed of the conductive fiber B) of the braided piezoelectric element 11 is connected to the input terminal of the amplifying unit 112, A braided piezoelectric element or conductive fiber 18 different from the braided piezoelectric element 11 connected to the input terminal of the amplifying means 112 is connected to the ground (earth) terminal. For example, as shown in FIG. 7, in the cloth-like piezoelectric element 15, the lead wire from the core portion 13 of the braided piezoelectric element 11 is connected to the input terminal of the amplifying means 112, and intersects and contacts the braided piezoelectric element 11. The conductive fiber 18 is grounded. Further, for example, as shown in FIG. 8, when a plurality of braided piezoelectric elements 11 are arranged in the cloth-like piezoelectric element 15, the lead wire from the core portion 13 of one braided piezoelectric element 11 is connected to the input terminal of the amplifying unit 112. The lead wire from the core portion 13 of another braided piezoelectric element 11 aligned with the braided piezoelectric element 11 is grounded (grounded).

  When expansion / contraction deformation occurs in the central axis direction of the braided piezoelectric element 11, the piezoelectric fiber A is deformed to generate polarization. In accordance with the arrangement of positive and negative charges generated by the polarization of the piezoelectric fiber A, movement of charges occurs on the lead line from the output terminal of the conductive fiber B forming the core portion 13 of the braided piezoelectric element 11. The movement of electric charge on the lead line from the conductive fiber B appears as a minute electric signal (that is, current or potential difference). That is, an electric signal is output from the output terminal in accordance with the electric charge generated when the elastic deformation is applied in the direction of the central axis of the braided piezoelectric element 11 (the direction of the central axis of the cylindrical shape where the piezoelectric polymer is disposed). Is output. The amplifying unit 112 and the electric signal are amplified, the output unit 113 outputs the electric signal amplified by the amplifying unit 112, and the transmitting unit 114 outputs the electric signal output from the output unit 113 to an external device (not shown). ).

  Since the device 110 of the present invention is flexible and can be used in either a string form or a cloth form, a very wide range of applications can be considered. Specific examples of the device 110 of the present invention include a touch panel, a human or animal surface pressure sensor, for example, a glove or a band, in the shape of a clothing, supporter, handkerchief or the like including a hat, gloves, or socks. Sensors that detect bending, twisting, and expansion / contraction of joints shaped like supporters. For example, when used for humans, it can be used as an interface for detecting contact and movement, collecting information on movement of joints and the like for medical purposes, amusement purposes, and moving lost tissues and robots. In addition, it can be used as a stuffed animal that imitates animals and humanoids, a surface pressure sensor of a robot, a sensor that detects bending, twisting, and expansion / contraction of a joint. In addition, it can be used as a surface pressure sensor or shape change sensor for bedding such as sheets and pillows, shoe soles, gloves, chairs, rugs, bags, and flags.

  Furthermore, since the device 110 of the present invention is in the form of braids or fabrics and is flexible, it can be used as a surface pressure sensor or shape change sensor by sticking or covering all or part of the surface of any structure. Can do.

  Furthermore, since the device 110 of the present invention can generate a sufficient electric signal simply by rubbing the surface of the braided piezoelectric element 11, it can be used for a touch input device such as a touch sensor, a pointing device, or the like. . Further, since the position information and shape information in the height direction of the measurement object can be obtained by rubbing the surface of the measurement object with the braided piezoelectric element 11, it can be used for surface shape measurement and the like.

  Hereinafter, the present invention will be described more specifically by way of examples. However, the present invention is not limited to these examples.

The fabric for piezoelectric elements was manufactured by the following method.
(Manufacture of polylactic acid)
The polylactic acid used in the examples was produced by the following method.
To 100 parts by mass of L-lactide (manufactured by Musashino Chemical Laboratory, Inc., optical purity 100%), 0.005 part by mass of tin octylate was added, and 180 ° C. in a reactor equipped with a stirring blade in a nitrogen atmosphere. Then, 1.2 times equivalent of phosphoric acid was added to tin octylate, and then the remaining lactide was removed under reduced pressure at 13.3 Pa to obtain chips to obtain poly-L-lactic acid (PLLA1). . The obtained PLLA1 had a mass average molecular weight of 152,000, a glass transition point (Tg) of 55 ° C., and a melting point of 175 ° C.

(Piezoelectric fiber)
PLLA1 melted at 240 ° C. was discharged from a 24-hole cap at 20 g / min and taken up at 887 m / min. This unstretched multifilament yarn was stretched 2.3 times at 80 ° C. and heat-set at 100 ° C. to obtain a multifilament uniaxially stretched yarn PF1 of 84 dTex / 24 filament. Further, PLLA1 melted at 240 ° C. was discharged from a 12-hole cap at 8 g / min and taken up at 1050 m / min. This unstretched multifilament yarn was stretched 2.3 times at 80 ° C. and heat-set at 150 ° C. to obtain a multifilament uniaxially stretched yarn PF2 of 33 dtex / 12 filament. These piezoelectric fibers PF1 and PF2 were used as piezoelectric polymers. The poly-L-lactic acid crystallinity, poly-L-lactic acid crystal orientation, and optical purity of PF1 and PF2 were measured by the methods described later and were as shown in Table 1.

(Conductive fiber)
Silver-plated nylon manufactured by Mitsufuji Corporation, product name “AGposs” 100d34f (CF1) was used as the conductive fiber B. The resistivity of CF1 was 250Ω / m.
Further, silver plated nylon manufactured by Mitsufuji Corporation, product name “AGposs” 30d10f (CF2) was used as the conductive fiber B and the conductive fiber 5. The conductivity of CF2 was 950 Ω / m.

(Insulating fiber)
The 84dTex / 24 filament drawn yarn IF1 and 33dTex / 12 filament drawn yarn IF2 manufactured by drawing polyethylene terephthalate after melt spinning were used as insulating fibers.

(1) Poly-L-lactic acid crystallinity X _homo :
The poly-L-lactic acid crystallinity X _homo was determined from crystal structure analysis by wide angle X-ray diffraction analysis (WAXD). In wide-angle X-ray diffraction analysis (WAXD), an X-ray diffraction pattern of a sample was recorded on an imaging plate under the following conditions by a transmission method using a Rigaku ultra 18 type X-ray diffractometer.
X-ray source: Cu-Kα ray (confocal mirror)
Output: 45kV x 60mA
Slit: 1st: 1mmΦ, 2nd: 0.8mmΦ
Camera length: 120mm
Integration time: 10 minutes Sample: 35 mg of polylactic acid fibers are aligned to form a 3 cm fiber bundle The total scattering intensity I _total is obtained over the azimuth angle in the obtained X-ray diffraction pattern, where 2θ = 16.5 °, 18 The sum ΣI _HMi of the integrated intensities of the diffraction peaks derived from the poly-L-lactic acid crystals appearing around .5 ° and 24.3 ° was obtained. From these values, poly-L-lactic acid crystallinity X _homo was determined according to the following formula (1).
[Equation 1]
Poly-L-lactic acid crystallinity X _homo (%) = ΣI _HMi / I _total × 100 (1)
Note that ΣI _HMi was calculated by subtracting diffuse scattering due to background and amorphous in the total scattering intensity.

(2) Poly-L-lactic acid crystal orientation degree A:
Regarding the poly-L-lactic acid crystal orientation degree A, in the X-ray diffraction pattern obtained by the above wide-angle X-ray diffraction analysis (WAXD), poly-L-lactic acid appears in the vicinity of 2θ = 16.5 ° in the radial direction. for diffraction peaks derived from crystals, taking the intensity distribution for azimuthal (°), it was calculated from the following equation (2) from the sum of the half-width of the resulting distribution profile .SIGMA.W i _(°).
[Equation 2]
Poly-L-lactic acid crystal orientation degree A (%) = (360−ΣW _i ) ÷ 360 × 100 (2)

(3) Optical purity of polylactic acid:
Collect 0.1 g of polylactic acid fiber (one bundle in the case of multifilament) constituting the fabric, add 1.0 mL of 5 mol / L sodium hydroxide aqueous solution and 1.0 mL of methanol, and heat to 65 ° C. Set in a set water bath shaker, hydrolyze for about 30 minutes until the polylactic acid becomes a homogeneous solution, and further neutralize to pH 7 by adding 0.25 mol / liter of sulfuric acid to the hydrolyzed solution. Then, 0.1 mL of the decomposition solution was collected, diluted with 3 mL of high-performance liquid chromatography (HPLC) mobile phase solution, and filtered through a membrane filter (0.45 μm). This adjustment solution was subjected to HPLC measurement, and the ratio of L-lactic acid monomer to D-lactic acid monomer was quantified. When the amount of one polylactic acid fiber is less than 0.1 g, the amount of other solution used is adjusted according to the amount that can be collected, and the concentration of polylactic acid in the sample solution used for HPLC measurement is 100 minutes from the above. It was made to be in the range of 1.

<HPLC measurement conditions>
Column: “Sumichiral (registered trademark)” OA-5000 (4.6 mmφ × 150 mm) manufactured by Sumika Chemical Analysis Co., Ltd.
Mobile phase: 1.0 mmol / liter copper sulfate aqueous solution Mobile phase flow rate: 1.0 ml / min Detector: UV detector (wavelength 254 nm)
Injection amount: 100 microliters When the peak area derived from the L-lactic acid monomer is S _LLA and the peak area derived from the D-lactic acid monomer is S _DLA , S _LLA and S _DLA are the molar concentrations M _LLA and L-lactic acid monomer. Since it was proportional to the molar concentration M _DLA of the D-lactic acid monomer, the larger value of S _LLA and S _DLA was taken as S _MLA , and the optical purity was calculated by the following formula (3).
[Equation 3]
Optical purity (%) = S _MLA ÷ (S _LLA + S _DLA ) × 100 (3)

(4) Orientation angle θ of the piezoelectric polymer with respect to the direction of the central axis
The orientation angle θ of the piezoelectric polymer with respect to the direction of the central axis was calculated from the following formula.
θ = arctan (2πRm / HP) (0 ° ≦ θ ≦ 90 °)
However, Rm = 2 (Ro ³ −Ri ³ ) / 3 (Ro ² −Ri ² ), that is, the radius of the piezoelectric structure weighted by the cross-sectional area. The helical pitch HP, the outer radius Ro and the inner radius Ri of the portion occupied by the piezoelectric structure were measured as follows.

(4-1) When the piezoelectric structure is a braided piezoelectric element (if the braided piezoelectric element is coated with a material other than the piezoelectric polymer, the coating is removed as necessary to remove the piezoelectricity from the side surface. Side view photographs were taken (after the polymer was in an observable state), and the helical pitch HP (μm) of the piezoelectric polymer was measured at any five locations as shown in FIG. Also, after impregnating the braided piezoelectric element with a low-viscosity instantaneous adhesive “Aron Alpha EXTRA2000” (Toagosei) and solidifying it, a cross section perpendicular to the long axis of the braid is cut out and a cross-sectional photograph is taken. As described later, the outer radius Ro (μm) and the inner radius Ri (μm) of the portion occupied by the piezoelectric structure are measured as described later. It was. When the piezoelectric polymer and the insulating polymer are assembled at the same time, for example, when a combination of piezoelectric fiber and insulating fiber is used, or when four fibers of 8-strand braid are high in piezoelectricity When the remaining four fibers are insulating polymers, when the cross section is taken at various locations, the region where the piezoelectric polymer is present and the region where the insulating polymer is present are interchanged. Therefore, the region where the piezoelectric polymer is present and the region where the insulating polymer is present are regarded as a portion occupied by the piezoelectric structure. However, a portion where the insulating polymer is not assembled at the same time as the piezoelectric polymer is not regarded as a part of the piezoelectric structure.

  The outer radius Ro and the inner radius Ri were measured as follows. As shown in the cross-sectional photograph of FIG. 9A, a region occupied by the piezoelectric structure (hereinafter referred to as PSA) and a region in the central portion of the PSA that is not PSA (hereinafter referred to as CA) are defined. Also, as shown in FIG. 9B, the average of the smallest perfect circle diameter that is outside the PSA and does not overlap the PSA and the largest perfect circle diameter that does not pass outside the PSA (CA may pass). Let the value be Ro. Further, as shown in FIG. 9C, an average value of the diameter of the smallest perfect circle that is outside the CA and does not overlap the CA and the diameter of the largest perfect circle that does not pass outside the CA is Ri.

(4-2) When the piezoelectric structure is a covering thread-like piezoelectric element, the winding speed when covering the piezoelectric polymer is T times / m (the number of rotations of the piezoelectric polymer per the length of the covering thread). In this case, the helical pitch HP (μm) was set to 1000000 / T. In addition, a low-viscosity instantaneous adhesive “Aron Alpha EXTRA2000” (Toagosei) was infiltrated into the covering yarn-shaped piezoelectric element and solidified, and then a cross-section perpendicular to the long axis of the braid was cut out and a cross-sectional photograph was taken. Regarding the cross-sectional photograph, the outer radius Ro (μm) and the inner radius Ri (μm) of the portion occupied by the piezoelectric structure are measured in the same manner as in the braided piezoelectric element, and the same measurement is performed at another arbitrary five cross sections. And averaged. When the piezoelectric polymer and the insulating polymer are covered at the same time, for example, when the piezoelectric fiber and the insulating fiber are covered, or the piezoelectric fiber and the insulating fiber do not overlap. If the cross section is taken at various locations, the region where the piezoelectric polymer is present and the region where the insulating polymer is present are interchanged with each other, so that the piezoelectric polymer exists. The region and the region where the insulating polymer exists are combined and regarded as a portion occupied by the piezoelectric structure. However, the insulating polymer is not covered simultaneously with the piezoelectric polymer, that is, the portion where the insulating polymer is always inside or outside the piezoelectric polymer regardless of the cross section, Not considered part of it.

(5) Electric signal measurement The electrometer (Keysight B2987A) is connected to the conductor of the piezoelectric element via a coaxial cable (core: Hi pole, shield: Lo pole). The current value was measured at intervals of 50 milliseconds while performing the operation test of any one of ˜5.

(5-1) Tensile test Using a universal testing machine "Tensilon RTC-1225A" manufactured by Orientec Co., Ltd., holding the piezoelectric element with a chuck at an interval of 12 cm in the longitudinal direction of the piezoelectric element, The displacement is set to 0.0 N, the displacement is set to 0 mm in the state pulled to the tension of 0.5 N, the operation is pulled up to 1.2 mm at an operation speed of 100 mm / min, and then returned to 0 mm at the operation speed of −100 mm / min 10 times. Repeated.

(5-2) Torsion test Of the two chucks that grip the piezoelectric element, one of the chucks is placed on a rail that does not twist and moves freely in the longitudinal direction of the piezoelectric element. .5N tension is always applied, and the other chuck uses a torsion test device designed to perform a torsional movement without moving in the longitudinal direction of the piezoelectric element, and is spaced 72 mm in the longitudinal direction of the piezoelectric element. Rotate from 0 ° to 45 ° at a speed of 100 ° / s so that the piezoelectric element can be gripped by these chucks and twisted clockwise when viewed from the center of the element (ie, the piezoelectric element twists in a Z twist) Then, the reciprocating torsional operation of rotating from 45 ° to 0 ° at a speed of −100 ° / s was repeated 10 times.

(5-3) Bending test Two chucks, upper and lower, are provided, the lower chuck is fixed, the upper chuck is positioned 72 mm above the lower chuck, and the line segment connecting the two chucks is the diameter. Using a test device in which the upper chuck moves on a virtual circumference, the piezoelectric element is held and fixed on the chuck, and the upper chuck is positioned at 12 o'clock and the lower chuck at 6 o'clock on the circumference. When the position is set, the piezoelectric element is slightly bent convexly in the 9 o'clock direction, and then the upper chuck is moved from the 12 o'clock position through the 1 o'clock and 2 o'clock positions on the circumference. The reciprocating bending operation of moving to the hour position at a constant speed over 0.9 seconds and then moving to the 12 o'clock position over 0.9 seconds was repeated 10 times.

(5-4) Shear test A 64 mm long portion of the central portion of the piezoelectric element is sandwiched horizontally from above and below by two rigid metal plates with a plain woven fabric woven with 50th cotton yarn on the surface. (The lower metal plate is fixed to the base.) A vertical load of 3.2 N is applied from the top, and the upper metal plate remains in a state where it does not slip between the cotton cloth on the surface of the metal plate and the piezoelectric element. Was pulled in the longitudinal direction of the piezoelectric element over 1 second from 0N to 1N load, and then the shearing operation for returning the tensile load to 0N over 1 second was repeated 10 times.

(5-5) Press test Using a universal testing machine "Tensilon RTC-1225A" manufactured by Orientec Co., Ltd., the portion of the length of the central part 64 mm of the piezoelectric element placed on a horizontal and rigid metal base is The piezoelectric element is sandwiched horizontally by a rigid metal plate installed on the crosshead, and the upper crosshead is lowered over 0.6 seconds until the reaction force from the piezoelectric element to the upper metal plate becomes 0.01N to 20N. Then, the operation of depressurizing over 0.6 seconds until the reaction force became 0.01 N was repeated 10 times.

(Braided piezoelectric element)
(Example 1)
As a sample of Example 1, as shown in FIG. 3, the conductive fiber CF1 is used as the core yarn, and among the eight carriers of the 8-punch round braid stringing machine, the above four carriers are assembled in the Z twist direction. The piezoelectric fiber PF1 is spirally formed around the core yarn by setting the insulating fiber IF1 on the four carriers assembled in the S twist direction. A braided piezoelectric element 1 wound around was prepared. The Ri, Ro, and HP of the braided piezoelectric element were measured, and the calculated values of the orientation angle θ of the piezoelectric polymer with respect to the direction of the central axis and the values of T1 / T2 are shown in Table 2. Ri and Ro were measured as the area occupied by the piezoelectric structure by combining the areas where the piezoelectric fibers and the insulating fibers exist in the cross section. The same applies to the braided piezoelectric element in the following examples.
The braided piezoelectric element 1 was cut to a length of 15 cm, the core conductive fiber was connected to an electrometer (Keysight B2987A) with the wire mesh shielding the periphery as the Hi electrode, and the current value was monitored. Table 2 shows current values in the tensile test, torsion test, bending test, shear test, and pressing test.

(Example 2)
The braided piezoelectric element 1 is used as a core yarn, and among the eight carriers of the string making machine, all of the four carriers assembled in the Z twist direction and the four carriers assembled in the S twist direction are filled with the conductive fiber CF2. The braided piezoelectric element 2 was manufactured by covering the braided piezoelectric element 1 with conductive fibers. The Ri, Ro, and HP of the braided piezoelectric element were measured, and the calculated values of the orientation angle θ of the piezoelectric polymer with respect to the direction of the central axis and the values of T1 / T2 are shown in Table 2.
The braided piezoelectric element 2 was cut to a length of 15 cm, the core conductive fiber was set as the Hi pole, and the sheath conductive fiber was set as the Lo pole and connected to an electrometer (Keysight B2987A), and the current value was monitored. Table 2 shows the current values of the torsion test, bending test, shear test, and pressing test during the tensile test.

(Examples 3 and 4)
Except for changing the winding speed of the PF 1, two braided piezoelectric elements are prepared in the same manner as the braided piezoelectric element 1, and these braided piezoelectric elements are used as core yarns, similarly to the braided piezoelectric element 2. What was covered with the conductive fiber was produced, and the braided piezoelectric elements 3 and 4 were obtained. The Ri, Ro, and HP of the braided piezoelectric elements 3 and 4 are measured, and the calculated values of the orientation angle θ of the piezoelectric polymer with respect to the direction of the central axis and the values of T1 / T2 are shown in Table 2.
The braided piezoelectric elements 3 and 4 are each cut to a length of 15 cm, and connected to an electrometer (Keysight B2987A) with the core conductive fiber as the Hi pole and the sheath conductive fiber as the Lo pole. Monitored. Table 2 shows the current values of the torsion test, bending test, shear test, and pressing test during the tensile test.

(Examples 5 to 8)
Among the eight carriers of the string making machine, PF1 or IF1 is set and assembled on the carriers assembled in the Z twist direction and the S twist direction as shown in Table 2, so that the Z twist direction and the S twist around the core yarn. A braided piezoelectric element in which the piezoelectric fibers PF1 are spirally wound at a predetermined ratio in each direction is created, and these braided piezoelectric elements are used as core yarns, and the braided piezoelectric element 2 is made of conductive fibers as in the braided piezoelectric element 2. What was covered was produced and it was set as braided piezoelectric element 5-8. Ri, Ro, and HP of the braided piezoelectric elements 5 to 8 are measured, and the calculated values of the orientation angle θ of the piezoelectric polymer with respect to the direction of the central axis and the values of T1 / T2 are shown in Table 2.
The braided piezoelectric elements 5 to 8 are each cut to a length of 15 cm, the core conductive fiber is set to Hi pole, and the sheath conductive fiber is set to Lo pole and connected to an electrometer (Keysight B2987A), and the current value is Monitored. Table 2 shows the current values of the torsion test, bending test, shear test, and pressing test during the tensile test.

Example 9
A braided piezoelectric element is created in the same manner as the braided piezoelectric element 1 except that PF2 is used instead of PF1, IF2 is used instead of IF1, and the winding speed is adjusted. A braided piezoelectric element 9 was prepared by forming a thread and covering with conductive fibers in the same manner as the braided piezoelectric element 2. Ri, Ro, and HP of the braided piezoelectric element 9 are measured, and the calculated values of the orientation angle θ of the piezoelectric polymer with respect to the direction of the central axis and the values of T1 / T2 are shown in Table 2.
The braided piezoelectric element 9 was cut to a length of 15 cm, the core conductive fiber was set as the Hi pole, and the sheath conductive fiber was set as the Lo pole and connected to an electrometer (Keysight B2987A), and the current value was monitored. Table 2 shows the current values of the torsion test, bending test, shear test, and pressing test during the tensile test.

(Example 10)
A braided piezoelectric element is prepared in the same manner as the braided piezoelectric element 1 except that IF2 is used instead of PF2 and PF2 is used instead of IF2, and the braided piezoelectric element is used as a core yarn. A braided piezoelectric element 10 was prepared by covering with conductive fibers in the same manner as in No. 2. The Ri, Ro, and HP of the braided piezoelectric element 10 are measured, and the calculated values of the orientation angle θ of the piezoelectric polymer with respect to the direction of the central axis and the values of T1 / T2 are shown in Table 2.
The braided piezoelectric element 10 was cut to a length of 15 cm, the core conductive fiber was set as the Hi pole, and the sheath conductive fiber was set as the Lo pole and connected to an electrometer (Keysight B2987A), and the current value was monitored. Table 2 shows the current values of the torsion test, bending test, shear test, and pressing test during the tensile test.

(Example 11)
CF1 is used as a core yarn, PF1 is wound around the core yarn in the S twist direction at a covering number of 3000 times / m, and IF1 is further wound around the outer side at a covering number of 3000 times / m in the Z twist direction. Further, CF2 is wound around the outer side with a covering speed of 3000 times / m in the S twist direction, and further CF2 is wound around the outer side with a covering number of 3000 times / m in the Z twist direction, and the S yarn is twisted around the core yarn. A covering yarn-like piezoelectric element 1 in which the piezoelectric fiber PF1 was spirally wound and the outer side was covered with a conductive fiber was produced. Ri and Ro of the covering yarn-like piezoelectric element are measured, and HP is obtained from the rotation speed (3000 times / m) at the time of manufacture, and the value of the orientation angle θ of the piezoelectric polymer with respect to the direction of the calculated central axis, and T1 / Table 2 shows the value of T2. Ri and Ro were measured as the area occupied by the piezoelectric structure in the cross-sectional area where the piezoelectric fiber was present. The same applies to the covering yarn-like elements in the following embodiments.
The covering yarn-like piezoelectric element 1 is cut to a length of 15 cm, and the core conductive fiber is connected to an electrometer (Keysight B2987A) as the Hi electrode and the sheath conductive fiber shielding the periphery as the Lo electrode. Was monitored. Table 2 shows current values in the tensile test, torsion test, bending test, shear test, and pressing test.

(Comparative Example 1)
A braided piezoelectric element was prepared in the same manner as the braided piezoelectric element 1 except that IF1 was used instead of PF1, and this braided element was used as a core thread and covered with conductive fibers in the same manner as the braided piezoelectric element 2. A braided element 1 was prepared. Since the piezoelectric polymer is not included, the values of θ and T1 / T2 cannot be measured.
The braided element 1 was cut to a length of 15 cm, the core conductive fiber was set to Hi pole, and the sheath conductive fiber was set to Lo pole and connected to an electrometer (Keysight B2987A), and the current value was monitored. Table 2 shows the current values of the torsion test, bending test, shear test, and pressing test during the tensile test.

(Comparative Example 2)
A covering thread-like element was prepared in the same manner as the covering thread-like piezoelectric element 1 except that IF1 was used instead of PF1. Since the piezoelectric polymer is not included, the values of θ and T1 / T2 cannot be measured.
The covering thread-like element 1 was cut to a length of 15 cm, and the electroconductive fiber (Keysight B2987A) was connected with the core conductive fiber as the Hi pole and the sheath conductive fiber as the Lo pole, and the current value was monitored. Table 2 shows the current values of the torsion test, bending test, shear test, and pressing test during the tensile test.

(Comparative Example 3)
A braided piezoelectric element 11 was prepared in the same manner as the braided piezoelectric element 2 except that PF1 was used instead of IF1. The Ri, Ro, and HP of the braided piezoelectric element 11 are measured, and the calculated values of the orientation angle θ of the piezoelectric polymer with respect to the direction of the central axis and the values of T1 / T2 are shown in Table 2.
The braided piezoelectric element 11 was cut to a length of 15 cm, the core conductive fiber was set as the Hi pole, and the sheath conductive fiber was set as the Lo pole and connected to an electrometer (Keysight B2987A), and the current value was monitored. Table 2 shows the current values of the torsion test, bending test, shear test, and pressing test during the tensile test.

(Comparative Example 4)
A braided piezoelectric element 12 was prepared in the same manner as the braided piezoelectric element 9 except that PF2 was used instead of IF2. Ri, Ro, and HP of the braided piezoelectric element 12 are measured, and the calculated values of the orientation angle θ of the piezoelectric polymer with respect to the direction of the central axis and the values of T1 / T2 are shown in Table 2.
The braided piezoelectric element 12 was cut to a length of 15 cm, and the current value was monitored by connecting the core conductive fiber as a Hi pole and the sheath conductive fiber as a Lo pole to an electrometer (Keysight B2987A). Table 2 shows the current values of the torsion test, bending test, shear test, and pressing test during the tensile test.

(Comparative Example 5)
Using the conductive fiber CF1 as the core yarn, among the 16 carriers of the 16 punched braided cord making machine, the piezoelectric fiber PF1 is set on 8 carriers assembled in the Z twist direction and assembled in the S twist direction. The braided piezoelectric element 13 in which the piezoelectric fiber PF1 was spirally wound around the core yarn in the Z twist direction was assembled by setting and assembling the above insulating fibers IF1 on the eight carriers. Ri and Ro of the braided piezoelectric element 13 are measured, and HP is obtained from the number of rotations (100 times / m) at the time of manufacture, and the calculated value of the orientation angle θ of the piezoelectric polymer with respect to the direction of the central axis, and T1 Table 2 shows the value of / T2.
The braided piezoelectric element 13 is cut to a length of 15 cm, the core conductive fiber is connected to an electrometer (Keysight B2987A) as the Hi electrode, and the sheath conductive fiber shielding the periphery is connected to the Lo electrode. Was monitored. Table 2 shows current values in the tensile test, torsion test, bending test, shear test, and pressing test.

(Comparative Example 6)
CF1 is used as a core yarn, PF1 is wound around the core yarn in the S twist direction at a covering number of 6000 times / m, and IF1 is further wound around the outer side at a covering number of 6000 times / m in the Z twist direction. Further, CF2 is wound around the outer side with a covering speed of 3000 times / m in the S twist direction, and further CF2 is wound around the outer side with a covering number of 3000 times / m in the Z twist direction, and the S yarn is twisted around the core yarn. A covering thread-like piezoelectric element 2 in which the piezoelectric fiber PF1 was spirally wound and the outer side was covered with a conductive fiber was produced. Ri and Ro of the covering yarn-like piezoelectric element 2 are measured, HP is obtained from the number of rotations (6000 times / m) at the time of manufacture, the value of the orientation angle θ of the piezoelectric polymer with respect to the direction of the central axis, and T1 Table 2 shows the value of / T2. The covering yarn-like piezoelectric element 2 is cut into a length of 15 cm, the core conductive fiber is set as the Hi pole, and the sheath conductive fiber shielding the periphery is connected as the Lo pole to the electrometer (Keysight B2987A), and the current value Was monitored. Table 2 shows current values in the tensile test, torsion test, bending test, shear test, and pressing test.

From the results of Table 2, when the orientation angle θ of the piezoelectric polymer with respect to the direction of the central axis is 15 ° or more and 75 ° or less and the value of T1 / T2 is 0 or more and 0.8 or less, it is large for the tensile operation. It can be seen that the device generates a signal and does not generate a large signal for an operation other than pulling, and selectively responds to the pulling operation. In addition, comparing Example 9 and Example 10, comparing the case where many piezoelectric fibers are wound in the Z twist direction and the case where many piezoelectric fibers are wound in the S twist direction, the signal polarity during the tensile test is It can be seen that the winding direction corresponds to the polarity of the signal.
Further, although not shown in the table, the elements of Examples 1 to 11 have a polarity opposite to each other and an absolute value approximately when the signal when the tensile load is applied is compared with the signal when the tensile load is removed. Since the same signal was generated, it can be seen that these elements are suitable for quantitative determination of tensile load and displacement. On the other hand, when the signals of the comparative examples 3 and 4 were compared with the signal when the tensile load was applied and the signal when the tensile load was removed, the polarity may be the opposite or the same. It can be seen that this element is not suitable for quantitative determination of tensile load and displacement.
Although not shown in the table, the noise level during the tensile test of Example 2 is lower than the noise level during the tensile test of Example 1, and a conductor is disposed outside the piezoelectric structure to provide a shield. It can be seen that noise can be reduced with the device.

DESCRIPTION OF SYMBOLS 1 Piezoelectric structure 1-1 Cylindrical piezoelectric structure 1-2 Cylindrical piezoelectric structure 2 Piezoelectric polymer CL Central axis OL Orientation direction HP Spiral pitch A Piezoelectric fiber B Conductive fiber 11 Braid shape Piezoelectric element 12 Sheath part 13 Core part 15 Fabric-like piezoelectric element 16 Fabric 17 Insulating fiber 18 Conductive fiber 110 Device 111 Piezoelectric element 112 Amplifying means 113 Output means 114 Transmitting means CL Fiber axis α Wound angle

Claims (12)

  A structure in which oriented piezoelectric polymers are arranged in a cylindrical or cylindrical shape, and the orientation angle of the piezoelectric polymer with respect to the direction of the central axis of the cylindrical or cylindrical shape in which the piezoelectric polymers are arranged is 15 ° or more. The piezoelectric polymer is 75 ° or less, and the piezoelectric polymer contains, as a main component, a crystalline polymer having an absolute value of the piezoelectric constant d14 of 0.1 pC / N or more and 1000 pC / N or less when the orientation axes are three axes. Further, the piezoelectric polymer includes a P body including a crystalline polymer having a positive piezoelectric constant d14 as a main component and an N body including a negative crystalline polymer as a main component, and the structure. For the portion having the central axis of 1 cm in length, the orientation axis is ZP, and the orientation axis is arranged by winding the spiral in the S twist direction. P body mass is SP, orientation axis is spiraled in Z twist direction The mass of the N-body arranged in this manner is ZN, the mass of the N-body arranged with the orientation axis wound in the S twist direction is SN, and the smaller one of (ZP + SN) and (SP + ZN) is T1 A structure whose value of T1 / T2 is 0 or more and 0.8 or less, where T2 is the larger one.   The structure according to claim 1, wherein the piezoelectric polymer includes poly-L-lactic acid or poly-D-lactic acid as a main component.   The structure according to claim 2, wherein the piezoelectric polymer includes a P body containing poly-D-lactic acid as a main component and an N body containing poly-L-lactic acid as a main component.   When stretching deformation is applied in the direction of the central axis of the cylindrical or columnar shape in which the piezoelectric polymer is disposed, charges having opposite polarities are generated on the central axis side and the outside of the cylindrical or columnar shape, The structure according to any one of claims 1 to 3.   5. The piezoelectric polymer according to claim 1, wherein the piezoelectric polymer is formed into a fiber, filament, or tape shape in a braided shape, a twisted cord shape, a covering yarn shape, or an aligned yarn shape. The structure described.   The structure according to any one of claims 1 to 4, wherein the piezoelectric polymer constitutes only one closed region in a cross section perpendicular to a cylindrical or columnar central axis.   An element comprising the structure according to claim 1 and a conductor disposed adjacent to the structure.    The element according to claim 7, wherein the piezoelectric polymer is disposed in a cylindrical shape, and the conductor is disposed at a position of a central axis of the cylindrical shape.   The element according to claim 8, wherein the conductor is made of a conductive fiber, and the piezoelectric polymer is arranged in a braid shape around the conductive fiber as a piezoelectric fiber.   The element of any one of Claims 7-9 which has arrange | positioned the said conductor on the outer side of the cylinder shape in which the said piezoelectric polymer is arrange | positioned.   The element according to claim 10, wherein the conductor is made of a conductive fiber, and the conductive fiber is arranged in a braid shape around a cylindrical shape in which the piezoelectric polymer is arranged. The device according to any one of claims 7 to 11,
An output terminal for outputting an electric signal generated in the conductor in response to an electric charge generated when the elastic deformation is given in the direction of the central axis of the cylindrical shape in which the piezoelectric polymer is disposed;
And an electric circuit for detecting an electric signal output via the output terminal.